Coil change

[Redbeard]

I have a set of zed ignition coils (possibly z1/900?) and leads in good condition but they read 2.3 and 2.6 ohms each, will they be ok on my ST which should have 3 ohm coils? Also, the ones I took off were mounted with the coil for 1 and 4 plugs on the right (sitting on the bike). It ran ok (except when wet hence the swap) so should I assume this is ok when I come to fitting new ones? Does it matter which leads go to which primary coil in other words? Leads are black/yellow and black for both sides, should I trace them right back to identify them as per the diagram?

[needaz1100r]

All that will matter when you re-assemble it is that the low tension, i.e. small, not plug lead, wires that went to the old 1/4 coil go to the new 1/4 coil.

Therefore it follows that the wires that went to the 2/3 coil go to the new 2/3 coil.

2.3 and 2.6 ohms is OK.

In my opinion.

the last bit is my opinion, the first two bits are fact.

[Redbeard]

Cheers Mark, that will do. Ta.

[zed1015]

Do not use coils of a lower resistance than recommended otherwise they will run hot, overheat and fail.
Higher is ok though.

[swampy]

the 2.3/2.6 coils are designed for bikes that left the factory with electronic ignition. wiith a bike that left the factory with points type ignition they need to use 3ohm coils other wise they will run hot make plugs breakdown and eventually fail as Zed has previously mentioned.

I know this to be fact as it has happened to me!

[PAULJAC47]

If in doubt just look at timing marks and see what points are opening at T/f 1 and 4 ,trace that wire to coil for pots 1 and 4 leads for ht side can go to either 1 or 4,then set left are for 2 and 3,agree dont use these coils for points set up 3 ohm to around 5ohm primary resitsance.

[swampy]

Just an additional aside, if your budget allows I would go for Dyna coils and Taylor leads as there output voltage is quite a bit higher than standard coils.
Producing a fatter cleaner spark, in turn this leads to easier starting and more efficient burn of fuel/air in the engine.

If you decided to go for an aftermarket electronic ignition (such as Dyna S or Newtronic for example) still use 3 ohm coils as they are designed for such, the exception being some digital ignitions. So do your research on those.

[Redbeard]

Ok guys. ST has electronic ignition not points but sounds like it is best avoided anyway. Cheers.

[chrisu]

Adam,

ST basically a Mk2 engine which has 1.5 Ohm coils as standard

Are you sure you've got 3 Ohm coils fitted ?

[Redbeard]

Hi Chris, yeah I checked the ones I have taken off and both read 3ohms. The Clymer manual states 1.5ohms is standard.
Wiredgeorge mentions a ballast resistor that would have been fitted originally but may have been removed if higher resistance coils are fitted, normally the 3ohm dyna coils. Is this a possibility? Z1E also mentions removal of this resistor this in the description of fitting dyna 3ohm coils. Also, out of interest how accurate are the resistances of coils compared with what they should be?

[chrisu]

Yes that assumes a balance resistor I think

[Pigford]

I made the mistake of running 1.5 ohm Dyna coils (grey) with a Dyna S on my Harris, when I first ran her up....... I had a spare set over from my old Z1000 which ran Dyna 2000 & could use 1.5 ohm. The grey coils lasted less than 100 miles until one melted

[KeithZ1R]

I have a ballast if you goin down that route

[Redbeard]

Thanks for the offer Keith, I will work things out first and see how I get on, might bite the bullet and go for dyna coils instead. Dunno yet.